High-temperature lubricating grease



Patented Apr. 11, 1950 HIGH-TEMPERATURE LUBRIOATING GREASE Harry W. Rudel, Roselle Park, and Arnold J. Morway, Clark Township, Union County, N. .L, assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application March 30, 1948, Serial No. 18,081

3 Claims.

The present invention relates to high temperature lubricating greases and particularly to greases of such type that are stabilized against oxidation. The invention relates further to means for stabilizing high temperature greases and particularly greases containing high percentages of the soaps of high molecular weight fatty oils or glycerides which normally are subject to rapid oxidation. This application is a continuation-in-part of a previous application, Serial No. 513,474, filed December 8, 1943. by the present inventors (now abandoned).

Numerous types of lubricating greases are known, most of them being based upon mineral lubricating oils thickened to a desired consistency by the use of metal soaps of fatty acids and fatty oils. At ordinary temperatures the grease compositions of this general character are not particularly subject to oxidation but for some purposes it is desirable to add to them substances which inhibit oxidations. The prior art contains numerous suggestions for the addition of antioxidants of various types. Thus the patent to Zimmer and Morway, No. 2,360,631, suggests that slightly alkaline greases containing an alkali metal soap of unsaturated fatty acid may be stabilized by addition of a small amount of saturated fatty acid soap or an amphoteric metal. This reference further suggests the use of a small amount of phenyl alpha naphthylamine as antioxidant and it suggests that other conventional addition agents may be added to greases of the type therein described, such as metal deactivators, extreme pressure agents, etc.

The prior art also contains numerous suggestions of compounds and compositions which are said to be useful as metal deactivators, i. e. to inhibit the catalytic efiect of certain metals on hydrocarbon fuels and oils. Thus U. S. Patent No. 2,285,878 to White and Walters described the stabilization of various refined and semi-refined hydrocarbon oils by incorporating therein certain copper deactivators. This patent indicates that certain oxygenated hydrocarbons reacted with certain primary amines are useful. In particular the patent shows that diacetyl acetone (or acetonyl) ethylene diamine is an efiective gum inhibitor in gasoline and, to a lesser extent, dibenzoyl acetone ethylene diamine is also effective.

The present invention involves an improvement over that described in the Zimmer and Morway patent which is applicable particularly to greases containing from 0.1 to about 2% excess alkali (as NaOH) along with substantial quantities of the alkali metal (especially sodium) snaps of fatty oils (glycerides). The excess alkali is added to enhance high temperature stability. Soaps of the fatty oils are to be distinguished from the soaps of fatty acids. The invention also relates to the use of dibenzoyl acetone condensed with a lower alkylene diamine as a potent stabilizer. As is well understood by those skilled in th art, the saponification of fatty oils results in the release of glycerin from the oil which, where the soap is formed in the oil, remains in the grease. unless particular steps are taken to remove the glycerin. While glycerin per se is not objectionable in greases, it does have a pronounced tendency to promote oxidation and this is particularly true at higher temperatures. Hence,- such a grease containing both free or excess alkali and the alkali metal soaps of fatty oils or glycerides tends to have poor resistance to oxidation, especially at higher temperatures. This is particularly true of greases having a high soap content and such greases have been found very diilicult to inhibit efiectively against oxidation under some conditions.

Oxidation in lubricating greases is especially objectionable because it results in the development of acidic bodies predominantly of low molecular weight which are definitely corrosive. This is particularly true of those greases which are designed for lifetime lubrication of ball bearings and the like or for any long continued use. A minor oxidation of a grease which is frequently replaced may be of no consequence, whereas oxidation in a grease that is intended to lubricate a bearing for life may be a very serious matter. Certain types of greases based upon the use of substantial proportions of the sodium and/or lithium or other alkali soaps of fats or fatty oils, for example, the unsaturated non-drying vegetable or animal fats and oils having 12 to 22 carbon atoms such as rape seed oil, mustard oil and the like. These have proved very suitable for long time or life time lubrication of bearings where the temperatures may become very high, provided they can be prevented from oxidizing. A specific object of the present invention is to staalkylene diamine and an oxidation inhibitor in an amount ranging from 0.1-1% thoroughly stabilizes an alkaline soap base grease of high soap content, e. g. to 40% soap by weight, against rapid deterioration at high working temperatures. Before addition to the grease, these aliphatic acyl acetophenone-alkylene diamine condensation products and the oxidation inhibitor may be compounded to any desired ratio, ,but it is preferred 4 Generically this type of condensation product falls within that class of compounds represented by the following empirical formula in which R represents an aromatic hydrocarbon radical such as phenyl, toluyl, etc., or any homologue thereof; R represents a monovalent alkyl hydrocarbon radical such as methyl, ethyl, etc.,

to utilize about equal parts by weight of antioxidant and condensation product. The greases may be compounded in the usual way, such as by melting the high molecular Weight fatty acids or corresponding'fats in a mineral lubricating oil and while in the molten state either neutralizing the'high molecular weight fatty acid or saponifying the corresponding fat with the desired hydrated metallic oxide using an excess of the hydrated oxideover that theoretically required for the reaction. At this point, the grease should be tested for free alkalinity and adjusted to contain from .1% to 2.0%, or 0.35%, which latter amount may be preferred, pf free alkali calculated as Na'OH. After the neutralization or saponification and alkali adjustment steps have been completed and while the grease is in the molten state, the combination of anti-oxidant and acetophenoneethylene diamine condensation product is incorporated into the molten grease by stirring, if the grease is to be cast into cakes. Otherwise it is preferable to cool the grease in the kettle to temperatures in the range of 300 F. (while stirring), adding the inhibitors in oil solution to prevent anydeterioration of the inhibitors at the high molten state temperatures. Also, if desired, the grease may be compounded by melting suitable soaps containing free alkali in the lubricating oil. After the mass is thoroughly fluid, andpreferably just prior to its removal from the cooking vessel, the stabilizing agents are stirred into the fluid grease which is then removed from the vessel. The grease additives of the present invention are well-known compounds and the methods of preparing the same are described in the literature. See also the White et al. patent mentioned above.

Among the oxidation inhibitors useful for the purpose of this invention there may be mentioned various alkylated phenols such as tertiar butyl meta cresol; phenol others such as the tertiary butyl ether of o-tertiary butyl, p-cresol; or aromatic amines such as phenyl alpha naphthylamine; etc., as representatives of this class of compounds. The other additives, complementary to the antioxidant, is a condensation product, resulting from the reaction between a polyamine,

and homologues thereof and R" represents a bivalent alkylenyl hydrocarbon radical such as ethylenyl, propylenyl, etc., and homologues thereof. Compounds of this class can be obtained by reacting aromatic acyl-substituted ketones such as benzoyl acetone; methyl benzoyl acetone; ethyl benzoyl acetone; benzoyl methyl ethyl ketone;

'benzoyl methyl propyl ketone; methyl benzoyl methyl ethyl ketone; ethyl benzoyl methyl ethyl I ketone, etc., with alkylene polyamines such as ethylene diamine; lzz-propylene diamine; 1:3-

preferably an alkyl diamine and an aliphatic ocnooomoom omcomoocflm on, urn-r;

A specific example of this propylene diamine, diethylcne triamine, triethylene tetramine, etc.

In order'to show the efficacy of the combination of this invention, the Norma-Hofiman bomb oxidation test for lubricating greases was chosen as the testing medium. The conditions of the test were: 110 pounds per square inch initial oxygen pressure, 210 F. bath temperature, and using copper catalyst (0.25 x1325 x .015 electrolytic copper sheet). The test was run noting the number of hours required to obtain a fi-pound drop in oxygen pressure. The time required to secure a 5-pound pressure drop is customarily designated as the oxidation induction period and most'recent specification includes 100 hours as the minimum oxidation induction period. A grease of the following composition was selected as the testing specimen:

rape seed oil sodium sulfonate NaOl-I Coastal oil (55 vis./210 F.)

' 50% phenyl alpha-naphthylamine The results of the Norma-Hoffman test using various additives complementary to the phenyl alpha-naphthylamine antioxidants are shown in the table below:

It will be noted that in this particular grease, the only highly effective metal deactivators tested were the dibenzoyl compounds. The disalicylalethylene diamine gave substantially no improvement over the blank grease. The salicyclal hydroxamic acid compound and the diacetonylethylene diamine compound gave minor improvement. The latter is indicated in the White et al. Patent No. 2,285,878, as being a very efiective gum inhibitor for gasoline, superior to the dibenzoyl compounds. Thereverse appears to be true in the type of grease described above.

In view of the foregoing data, which indicated that the: dibenzoyl acetone condensed with lower alkylene diamines (ethylene or propylene)" was: specifically effective irr lrigh. soap content alkaline grease, the condensation product of dibenzoyl 6 of atleast 0.1% and not more than about 1 0% of the deactivator these percentages being by weight based onthe total composition.

The metal deactivators shown in the last three lines of the table were al'most'if not entirely inacetone with ethylene diamine being particularly eiiectwe, greases conta ning them showing 1 no e'fi'ective', an extensive series or tests was conimprovement over those containing no deactivaducted with. the results set forth in Table II. tor whatsoever. The grease in each case was a slightly alkaline The reasons for the specific effectiveness of grease (about 0.35% as free N'aOH) containing 10 benzoyl acetone condensed with a lower alkylene approximately by weight of sodium soap of diamine are not known. It appears to be clearly rape seed oil in a Coastal oil of about 55 S. S. U. established, however, that alkaline greases conviscosity at 210 F. The antioxidant used was taining 20% and more, up to or of phenyl alpha naphthylamine. The latter is prefsoaps of fatty oils, saponified in the oil so as to erably used in concentrations of 0.1 to 2%, 0.5 15 leave glycerine in the composition, present a to 1% being especially preferred, but in some peculiar problem in deactivation. This is doubtcases it may be omitted altogether. less due in part to their glycerine content (or Table II Antioxb Oxidation 0! Alkaline Grease Hours For Pressure Drop dent (Wt.

Percent) Metal Deactivator (Wt. Per Cent) 1# s14 10# 1514 20# 251; 301

0.5 74 so 106 118 130 0.5 37 as 107 111 119 13a 0.5 s so 92 114 134 0.5 18 so 116 138 160 178 0.5 10 as 1.0 so 88 132 170 214 230 1.0 1s 84 131 103 191 215 0.5 s 14 109 134 162 186 202 0.5 so 112 134 13s 158 160 0.5 s4 94 12s 15s 178 190 0.5 26 90 134 1.0 84 118 134 148 160 17s 0.5 0 00 246 280 204 310 320 334 0.5 o 50 248 304 320 330 342 0.5 0.2% Benzoylacetone+Ethylene Die-mine 84 148 172 194 210 220 228 0.5 0.1% Benzoylacetone-l-Ethylenc Diamine. 110 152 176 184 200 214 1.0 0.5 Benzoylacetone+Ethylene Diamine 64 222 260 274 286 1.0 0.1+ Benzoylaeetone-l-Ethylene Diamine 84 164 178 194 206 0.5 0.5% Benzoylacetonc-l-Propylene Diamine 80 164 190 212 226 234 246 0.5 do 84 140 170 188 198 214 220 0.5 0.5% Benzoylacetone+Diethylene Triamine 26 64 86 110 128 138 154 0.5 0.5% Benzoylacetone+lsobutyl Amine 14 54 82 98 112 122 134 0.5 0.5% Dibenzoylmethane-i-Ethylene Diamine 6 60 96 116 136 146 It will be noted from the foregoing table that derivatives thereof) and may be due in part also various metal deactivators known in the prior to the free alkali which is present. art and used hitherto as successful antioxidants It will be understood, therefore, that the inin gasoline, for example, and even in lubricating 45 vention contemplates the use of a specific type ils. hav d v difi r t y w us d i h of stabilizer for alkaline greases of high soap 8001) Content grease- It hpp o Various content where the soap is formed from fats or a a that have been obtamad that greases glycerides. It has specific application to those tamin 20% or or f a ah metal s p o fatty greases containing about 20% or more by weight Oils (Where lycerin is pr s t are p f rly 50 of the alkali metal soaps of rape seed oil and dlfficult to deactlvate 111111191? for hlgh related unsaturated oils. The lubricating oil may p j The condensation Product Of vary in viscosity and in viscosity index and varsahcylalqehrde and ethylene dlamme P ious other additives such as stringiness and pylene dlamme gave Poorer results in some tackiness agents, extreme pressure agents, etc., stances than no deactivator. Sahcyl hydroxamic 55 may be included as will be apparent to those acid and isooctyl salicylhydroxamic acid, both of Skilled in the art which have been suggested as effective deactivat rm 0 t A t 1 What is claimed 1s. v .212 rises: starrin tars A y essentially of mineral base lubricating oil con- 1n the prior art to be an effective inhlbitor for 60 gum in gasoline showed no appreciable improvetammg 20 to 40% by welght of the sodmm Soap ment. Even where the quantity of antioxidant f ip i Bald i l g z i was increased to 1.0%, the improvement was s an 1a g ycerme en an a con en of only moderate to 2% excess alkali calculated as free sodium On the other hand, the condensation product 65 hyqroxlde, to 2% Phenyl alpha naphthyl' of benzoyl acetone and ethylene diamine was amine, and0.1 to 1% of dibenzoyl acetone alkylene very fiectiv in a concentration of 05% and diamine wherein the alkylene group is selected even in concentrations as low as 0.1% it showed from the group conslstmg of ethylene and P a greater oxidation life for a 5 lb. drop in oxygen pylenepressure than 0.5% of any of the other metal 70 2. A lubricating grease compositio i tm deactivators. The related propylene diamine derivative also showed up pretty well, both being substantially superior in the 5 lb. drop test which is the most significant, to all other metal deactivators. This invention contemplates the use essentially of mineral base lubricating oil, about 30% by weight of sodium soap of rape seed oil said composition having a. substantial glycerine content and having excess alkalinity of about 0.35% calculated as free sodium hydroxide, 0.5

2,5 8 96 7 to 1% phenyl alpha. naphthylamine, and 0.1 to REFERENCES CITED O'5%-'dibenzy1acetne ethylene f The following references are of record in the 3. A lubricating grease composition consisting file of this patent: essentially of mineral base lubricating oil, about 30% by weight of sodium soap of rape seed oil 5 UNITED STATES PATENTS said composition having a substantial glycerine Number Name Date content and having excess alkalinity of about 2,265,791 Zimmer et a1 Dec. 9, 1941 0.35%, calculated as free sodium hydroxide, 0.5 2,285,878 White et a1 June 9, 1942 to 1% phenyl alpha naphthylamine, and 0.1 to 2,289,748 Beerbower et a1, July 14; 1942 0.5%. dibenzoyl acetone propylene diamine. 10 2,340,438 Strawn Feb. 1, 1944 v HARRY W. RUDEL. 2,360,631 Zimmer et al Oct. 17, 1944 ARNOLD J MORWAY. 

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF MINERAL BASE LUBRICATING OIL CONTAINING 20 TO 40% BY WEIGHT OF THE SODIUM SOAP OF RAPESEED OIL, SAID COMPOSITION HAVING A SUBSTANTIAL GLYCERINE CONTENT AND A CONTENT OF 0.25 TO 2% EXCESS ALKALI CALCULATED AS FREE SODIUM HYDROXIDE, 0.1 TO 2% PHENYL ALPHA NAPHTHYLAMINE, AND 0.1 TO 1% OF DIBENZOYL ACETONE ALKYLENE DIAMINE WHEREIN THE ALKYLENE GROUP IS SELECTED FROM THE GROUP CONSISTING OF ETHYLENE AND PROPYLENE. 